The disclosed technology relates to a lubricant for an internal combustion engine comprising, among other components, a nitrogen-functionalized olefin polymer.
Lubricants for internal combustion engines, such as spark-ignited engines for passenger cars, must meet demanding performance requirements. They must lubricate the engine to prevent wear and minimize friction, while being resistant to degradation and deterioration in performance arising from contact with combustion byproducts and other contaminants. In particular, it remains a challenge to provide lubricants that do not deteriorate over time by formation of sludge, varnish, or other deposits; this is often accomplished, at least in part, by including in the lubricant nitrogen-containing dispersants such as succinimide dispersants. It is also desirable that the lubricant should be resistant to deleterious effects arising from the presence of water, which may arise as a product of combustion of the fuel within the engine. The technology disclosed herein permits formulation with reduced amounts of nitrogen-containing succinimide dispersant while retaining good sludge and deposit prevention performance and providing good water tolerance.
U.S. Pat. No. 7,790,661, Covitch et al., Sep. 7, 2010, discloses dispersant viscosity modifiers containing aromatic amines. There is disclosed the reaction product of a polymer comprising carboxylic acid functionality or a reactive equivalent thereof, said polymer having a number average molecular weight of greater than 5,000, and an amine component comprising 3-nitroaniline. The aromatic amine can also be an N,N-dialkylphenylenediamine such as N,N-dimethyl-1,4,-phenylenediamine. Suitable backbone polymers include ethylene propylene copolymers. An ethylenically unsaturated carboxylic acid material is typically grafted onto the polymer backbone. Maleic anhydride or a derivative thereof is suitable. Conventional lubricant additives may also be present, including additional dispersants, detergents, and other materials. The derivatized graft copolymer can be employed in crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines.
U.S. Publication 2010/0162981, Adams et al., Jul. 1, 2010, discloses a multigrade lubricating oil composition with enhanced antiwear properties for use in an internal combustion engine, preferably a diesel engine. The lubricant comprises a base oil, one or more dispersant viscosity modifiers in a total amount of 0.15 to 0.8% by weight, one or more dispersants in a total amount of active dispersants of 1.5 to 3% by weight, one or more detergents, and one or more metal dihydrocarbyl dithiophosphates. An example of a suitable dispersant viscosity modifier is a co-polymer of ethylene-propylene grafted with an active monomer, for example maleic anhydride and then derivatized with an alcohol or amine. A suitable dispersant modifier is that present in Lubrizol's LZ 7177B.
U.S. Pat. No. 5,264,140, Mishra et al., discloses a lubricating oil composition comprising a major amount of a base oil and a minor amount of, as an antioxdant/dispersant VI improver additive, a lubricant additive. Disclosed is a polymer prepared from ethylene and propylene; an ethylenically unsaturated carboxylic acid material is grafted onto the polymer backbone. Maleic anhydride grafted polyisobutylene may also be used. The intermediate is reacted with an amino aromatic compound.
U.S. Publication 2009/0176672, Goldblatt, Jul. 9, 2009, discloses functional monomers for grafting to low molecular weight polyalkenes and their use in preparation of dispersants and lubricating oil compositions. The polyalkene may have an average molecular weight range of about 300 to about 10,000.
U.S. Publication 2011/0245119, Sauer, Oct. 6, 2011, discloses multiple function graft polymers useful as dispersants, suitable for controlling sludge, varnish, soot, friction, and wear. The polymer may have a molecular weight of from about 10,000 to about 500,000. A graftable coupling group may undergo condensation reaction with an amine. The products are said to be useful for internal combustion engines. The lubricants optionally may contain about 0.1 to about 10% of one or more detergents, preferably 0.5 to 4%.